Variable-drive hydraulic transmission for the fountain and ductor roll assemblies of an offset printing press

ABSTRACT

A hydraulic transmission is disclosed through which the fountain and ductor roll assemblies of an offset printing press are variably driven from a reciprocable drive mechanism having a constant stroke. The transmission allows for infinite variation in the angular motion of the respective rolls, and includes a pair of hydraulic cylinders which are connected in a closed hydraulic circuit, so that one piston of the cylinders is displaced by the drive mechanism, whereas the other piston is displaced by means which alternately yield to the counterstroke of the aforesaid other piston during the displacement of the one piston. By adjusting the volumetric capacity of the circuit, within a selected maximum pressure, the counterstroke of the aforesaid other piston is varied until it produces the angular motion desired for the rolls.

United States Patent Perrault et al. Aug. 29, 197 2 [54] VARIABLE-DRIVEHYDRAULIC 2,882,686 4/1959 Griffith ..60/54.5 TRANSMISSION FOR THEFOUNTAIN 2,544,134 3/1951 Clark ..60/54.5

AND DUCTOR ROLL ASSEMBLIES OF AN OFFSET PRINTING PRESS PrimaryExaminer-Martin P. Schwadron Assistant Examiner--A. M. Zupcic [72]Inventors: Delphus Eugene Perrault; Frederick AttomWJhristensen & SanbomRalph SchOPP, both of Seattle, Wash- 57 ABSTRACT [73] Assignee: webPress m Seattle A hydraulic transmission is disclosed through whichwashthe fountain and ductor roll assemblies of an offset [22] Filed;March 6, 1970 printing pressare variably driven from a reciprocabledrive mechanism having a constant stroke. The transl PP 17,258 missionallows for infinite variation in the angular motion of the respectiverolls, and includes a pair of 52 0.8. CI. ..60/54.5 R, 60/51 hydrauliccylinslers which are F 5 [51] Int. Cl ..F15b 7/00 hydrauhc so that oneplston of the cymders I displaced by the drive mechanism, whereas theother [58] Field of Search ..60/54.5 R

piston is displaced by means which alternately yield to 6 thecounterstroke of the aforesaid other piston during [5 1 1 ReferencesCited the displacement of the one piston. By adjusting the UNITED STATESPA'IENTS volumetric capacity of the circuit, within a selected maximumpressure, the counterstroke of the aforesaid BlIdl'Ol'Il R other pismnis i produces the angular 2,978,044 4/ 1961 Barnes ..60/54.5 tiondesired for the 1.011s. 2,597,050 5/1952 Audemar ..60/54.5 3,266,2178/1966 Van Den Bos ..60/54.5 4 Claims, 2 Drawing Figures FIELD OF THEINVENTION This invention relates to hydraulic transmissions, and

in particular to a hydraulic transmission for driving the fountain andductor roll assemblies of an offset printing press.

OBJECTS OF THE INVENTION A principal object of the present invention isto devise a hydraulic transmission which can variably drive the fountainand ductor roll assemblies of an offset printing press from areciprocable drive mechanism having a constant stroke. Another object isto provide a transmission of this nature wherein the angular motion ofthe rolls is infinitely variable. A further object is to provide atransmission of this nature which can be used to rotate the fountainrolls intermittently and unidirectionally; while simultaneously rockingthe ductor rolls through a continuous reciprocable motion. Still furtherobjects include providing a transmission of this nature which has adashpot effect on the assemblies of rolls, that is, the effect ofabsorbing irregularities in the operation of the same. Still furtherobjects will become apparent from the description of the invention whichfollows hereafter.

SUMMARY OF THE INVENTION These objects are realized by a hydraulictransmission of our invention which includes a circuit or conduitcharged with hydraulic fluid, and means closing the conduit to theescape of fluid therefrom, including a pair of hydraulic cylindersconnected therewith, the pistons of which are displaceable in relationto the conduit to apply pressure to the fluid therein. It also includesa constant-stroke reciprocable drive mechanism which is operable todisplace one piston against the fluid, and alternately to positivelyretract therefrom; and means which are operable to displace the otherpiston against the fluid during the retraction of the drive mechanism,and alternately to yield to the counter-stroke of the other pistonduring the displacement of the one piston. In addition, there are meanswhich are operable to adjust the volumetric capacity of the conduit, forpurposes of varying the counterstroke of the aforesaid other piston asdesired.

The transmission may be used to transmit intermittent uni-directionalpulses to a driven member, as for example, the fountain rolls of anoffset printing press; or it may be used to impart continuousreciprocable motion to a driven member, as for example,the ductor rollsof such a press; or it may be used to do both. In the first instance,the pulses are preferably transmitted to the driven member through aone-way clutch that is connected with the aforesaid other piston in thetransmission. In the other instances, the transmission preferablyfurther comprises a second conduit which is similarly charged withhydraulic fluid, and closed to the escape of fluid therefrom by meanswhich include a second pair of hydraulic cylinders connected therewith,the pistons of which are displaceable in relation to the second conduitto apply pressure to the fluid therein. The drive mechanism is employedin a doubleacting manner to displace one piston of the second conduit,against the fluid therein, while positively retracting from thecompressed fluid of the first-recited conduit, and vice versa. Moreover,the means for displacing the other piston of the first-recited conduit,include a counter-driven reciprocable member which is operable todisplace the other piston of the second conduit, while yielding to thecounterstroke of the aforesaid other piston of the first-recitedconduit, and vice versa.

In the preferred embodiments of the uni-directional drive arrangement,the one-way clutch is connected with the aforesaid other piston of thetransmission through a rack and pinion mechanism thereon. The means fordisplacing the other piston include a resilient member which is operableto yieldably bias the other piston against the fluid in the conduit. Inthe doubleconduit reciprocable drive arrangements, the counterdrivenreciprocable member preferably takes the form of a rocker arm which ismounted in connection with the aforesaid other pistons of the twoconduits, to pivot to and fro as the pistons reciprocate. Preferably,the rocker arm is connected with the pistons through ball and socketjoints thereon.

In all instances, the transmission preferably also comprises means forregulating the pressure of the fluid in the conduit or conduits within aselected maximum pressure, while maintaining the adjusted volume of theconduits. This latter means may include a third pairof hydrauliccylinders connected with the conduits, each of which includes a valvethat is resiliently loaded to close the aforesaid connection with theconduit, against the pressure therein, and a piston that is selectivelyoperable to vary the loading on the valve; there being a separateconnection with each conduit from its aforesaid regulator cylinder whichhas a valve therein that is closed by the pressure of the conduit, and aresiliently loaded hydraulic ram interconnected between the regulatorcylinders to equalize the hydraulic pressures therein.

BRIEF DESCRIPTION OF THE DRAWINGS These features will be better Iunderstood by reference to the accompanying drawing wherein:

FIG. 1 is a part-perspective view of one of the fountain and ductor rollassemblies in an offset printing press, together with the driveconnections from the transmission in FIG. 2; and

FIG. 2 is a schematic representation of the transmission as it is usedto drive both roll assemblies.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to thedrawing, it will be seen that each assembly of rolls includes a fountainroll 2 which picks up either ink or water in sweeping through a vat 4 ofthe same, and transfers the liquid to a ductor roll 6 which transfers itin turn to a distribution roll 8. The fountain roll 2 is rotated insuccessive intermittent unidirectional angular pulses through the mediumof a spring loaded rack and pinion mechanism 10 which is disposedopposite one end of the roll, and interconnected with it by a one-wayclutch 12. The ductor roll 6 is mounted in such a way as to bereciprocable through an arcuate path, the limits of "which are thepoints at which the roll makes surface contact with the fountain roll 2on one hand, and the distribution roll 8 on the other. The rockingmotion of the ductor roll is generated through an inverted T-shapedrocker arm 14 on which the roll is freely journaled at one end.Moreover, in operation, the motion of the roll is correlated with theangular advance of the fountain roll 2 so that the ductor roll iscontinually exposed to fresh liquid on contact with the fountain roll,and in addition is given a degree of rotation by such contact to assurethat fresh liquid is continually transferred to the distribution roll,which, of course, also imparts rotation to the ductor roll when the twolatter rolls make contact with one another.

Since two roll assemblies are involved, there are in fact, two rack andpinion mechanisms 10 and two rockers 14 between them; and according tothe invention, all are driven by a rotating eccentric or cam 16 (FIG. 2)which is interconnected with the two assemblies through the medium of apair of cooperatively arranged hydraulic transmissions 18 illustrated inFIG. 2. The transmissions 18 each include a system of conduits 20 whichare charged with hydraulic fluid and have a plurality of hydrauliccylinders 22 connected therewith. The cylinders are in communicationwith only the fluid in the conduits of that transmission, so that eachtransmission is closed to the escape of fluid therefrom. One of thecylinders 22r in each transmission is connected with one of the rack andpinion mechanisms 10, as is schematically illustrated to the right-handside of FIG. 2. Two other cylinders 22p in each transmission areconnected with corresponding legs of the two rockers 14 in the twoassemblies of rolls, so that between them, the two transmissions operateboth rockers in the assemblies of rolls. See the schematicrepresentation of the rockers at the top and bottom of FIG. 2. Inaddition, a fourth cylinder 22a in each transmission serves as means forregulating or adjusting the volume of fluid in the system of conduits ofthat transmission. And finally, the remaining cylinders of thetransmissions operate either as alternately reciprocable drive cylinders22d, or as mutually dependent hydraulic accumulators 220 which regulatethe pressures in the transmissions, and in addition make it possible tobalance the transmissions for smooth operation of the rolls.

Referring now in detail to FIG. 2, it will be seen that each system ofconduits comprises a main pressure transmission line 24, 25 whichinterconnects the rack v and pinion cylinder 22r of that transmission,with the drive cylinder 22d therein. Each regulator cylinder 22a isconnected with the main line 24, 25 through a branch line 26; and eachsystem also includes four laterals 28, 30, 32, 34, two 28 and 30 ofwhich operate to interconnect the main line 24, 25 with opposite sidesof the accumulator 22c, and the other pair 32 and 34 of which operatesto interconnect the main line 24, 25 and the branch line 26,respectively, with the rocker cylinder 22p. In each accumulator 220,there is an open-ended pressure chamber 36 which is closed at one end byan adjustment screw 38 threadedly interconnected therewith, and at theother end by a ball valve 40 which is resiliently loaded against thepressure in one of the accumulator laterals 28, by a spring 42 that iscaged between the valve 40 and the screw 38. The pressure chamber 36also has a connection 44 with the other lateral 30, and intermediate thetwo is a second ball valve 46 which ,is retained in closure position bythe pressure in the other lateral 30. The connection 44 also opens ontoa spring-loaded ram 48, the spring 50 of which is shared between the twotransmissions as illustrated.

In each regulator 22a, there is a fluid reservoir 51 which communicateswith the branch line 26 through a fixed plunger 52. The reservoir isfilled with the fluid and varies in volume depending on the longitudinalposition of a cap 53 which is threaded onto the plunger 52 to beadjusted longitudinally thereof.

In operation, the cam 16 is powered through the shaft 54 thereof, todrive the follower pistons 55 in the drive cylinders 22d in alternatesequence against the fluid in their respective transmissions. Theresultant compressive force in each transmission is transmitted in turnto the pistons 56 of the rack and pinion cylinders 22r and to thepistons 58 of the cylinders 22p serving the rockers. The former 56 aredirectly connected with the racks 56 of the mechanisms, and areresiliently loaded by springs 59; whereas the latter 58 have ball andsocket connections 60 with the rockers In order to vary the strokes ofthe racks and the rocker pistons in the respective transmissions, andthus of the fountain and ductor rolls themselves, the volumetriccapacity of either or both transmissions is varied by turning the caps53 of the regulator cylinders 22a longitudinally toward or away from theplungers 52. The resulting change in the counterstroke of each followerpiston 55 during the retraction of the cam, has the effect of alteringthe point at which the progressively more eccentric condition of the cam16 begins to exert the compressive effect on the fluid of thattransmission; and thus the point from which pressure is transmittedthrough the transmission to cause a change in the position of the rackor rocker pistons. The pressures of the transmissions are controlled,however, within the limits of the rack and rocker pistons, by theaccumulators. Therefore, should the pressure of either transmissionexceed a predetermined limit set by the adjustment screw 38, then theexcessive pressure is relieved by the opening of the ball valve 40 inthat transmission, and the surge of fluid into the accumulator isabsorbed by the spring loading 50 on the rams, until the pressure in thetransmission is equalized across the secondary ball valve 46 in thereturn connection 44, 30. In the final analysis, therefore, the twoaccumulators also serve as a means for balancing the two transmissions,inasmuch as the surge of one is absorbed in the other through thedouble-acting spring loading 50 therebetween.

A reciprocable drive mechanism other than the illustrated eccentric 16can be employed to achieve the double-acting wiper action of the same.For example, other cam means such as a three-lobed cam, can besubstituted for the eccentric.

Similarly, other modifications and additions can be made in and to theinvention without departing from the scope and spirit of the same asdefined in the following claims.

We claim as our invention:

1. In a hydraulic transmission, a pair of separate conduits each chargedwith a hydraulic fluid, means closing the conduits to the escape offluid therefrom, including a pair of hydraulic cylinders connected witheach conduit, the pistons of which cylinders are displaceable inrelation to the respective conduit to apply pressure to the fluidtherein, a constant stroke reciprocable drive mechanism operable todisplace one piston of one conduit against the fluid therein, whilepositively retracting from one piston of the other conduit, andalternately to displace the one piston of the other conduit against thefluid therein, while positively retracting from the one piston of theone conduit, means operable to displace the other piston of each conduitagainst the fluid therein, during the retraction of the drive mechanismwith respect to the aforesaid one piston thereof, and alternately toyield to the counterstroke of the respective other piston during thedisplacement of the one piston by the drive mechanism, the one piston ofeach conduit being counterstroked solely by the fluid in the respectiveconduit, during the displacement of the respective other piston thereof,and there being means operable to vary the volumetric capacity of eachconduit, hydraulic accumulator means operable to maintain the pressureof the fluid in each conduit, within a selected maximum pressure, whilemaintaining the adjusted volume of the respective conduit, and whereinthe hydraulic accumulator means includes a pair of hydraulic regulatorcylinders connected with the respective conduits, each of whichregulator cylinders includes a valve that is resiliently loaded to closeits connection with the respective conduit, against the pressuretherein, and means selectively operable to vary the loading on thevalve, there being a separate connection with each conduit from itsaforesaid regulator cylinder, which has a valve therein that is closedby the pressure of the respective conduit, and a resiliently loaded,double-acting hydraulic ram interconnected between the regulatorcylinders to equilize the hydraulic pressures therein.

2. The hydraulic transmission according to claim 1 wherein the means fordisplacing the other piston of each conduit, includes a resilient memberin connection with each of the aforesaid other pistons, to yieldablybias the same against the fluid in the respective conduits.

3. The hydraulic transmission according to claim 1 wherein the aforesaidother piston of each conduit has a one-way clutch connected therewith,to transmit intermittent unidirectional pulses to a driven member.

4. The hydraulic transmission according to claim 1 wherein the means fordisplacing the other piston of each conduit, includes a rocker memberwhich is operable to displace the other piston of the one conduit, whileyielding to the counterstroke of the other piston of the other conduit,and alternately to displace the other piston of the other conduit, whileyielding to the counterstroke of the other piston of the one conduit.

1. In a hydraulic transmission, a pair of separate conduits each chargedwith a hydraulic fluid, means closing the conduits to the escape offluid therefrom, including a pair of hydraulic cylinders connected witheach conduit, the pistons of which cylinders are displaceable inrelation to the respective conduit to apply pressure to the fluidtherein, a constant stroke reciprocable drive mechanism operable todisplace one piston of one conduit against the fluid therein, whilepositively retracting from one piston of the other conduit, andalternately to displace the one piston of the other conduit against thefluid therein, while positively retracting from the one piston of theone conduit, means operable to displace the other piston of each conduitagainst the fluid therein, during the retraction of the drive mechanismwith respect to the aforesaid one piston thereof, and alternately toyield to the counterstroke of the respective other piston during thedisplacement of the one piston by the drive mechanism, the one piston ofeach conduit being counterstroked solely by the fluid in the respectiveconduit, during the displacement of the respective other piston thereof,and there being means operable to vary the volumetric capacity of eachconduit, hydraulic accumulator means operable to maintain the pressureof the fluid in each conduit, within a selected maximum pressure, whilemaintaining the adjusted volume of the respective conduit, and whereinthe hydraulic accumulator means Includes a pair of hydraulic regulatorcylinders connected with the respective conduits, each of whichregulator cylinders includes a valve that is resiliently loaded to closeits connection with the respective conduit, against the pressuretherein, and means selectively operable to vary the loading on thevalve, there being a separate connection with each conduit from itsaforesaid regulator cylinder, which has a valve therein that is closedby the pressure of the respective conduit, and a resiliently loaded,double-acting hydraulic ram interconnected between the regulatorcylinders to equilize the hydraulic pressures therein.
 2. The hydraulictransmission according to claim 1 wherein the means for displacing theother piston of each conduit, includes a resilient member in connectionwith each of the aforesaid other pistons, to yieldably bias the sameagainst the fluid in the respective conduits.
 3. The hydraulictransmission according to claim 1 wherein the aforesaid other piston ofeach conduit has a one-way clutch connected therewith, to transmitintermittent unidirectional pulses to a driven member.
 4. The hydraulictransmission according to claim 1 wherein the means for displacing theother piston of each conduit, includes a rocker member which is operableto displace the other piston of the one conduit, while yielding to thecounterstroke of the other piston of the other conduit, and alternatelyto displace the other piston of the other conduit, while yielding to thecounterstroke of the other piston of the one conduit.